Dark Energy Survey
The Dark Energy Survey ( DES ) is a heaven screenable in the optical and near-infrared spectral range . Its main goals are the exploration of the accelerated expansion of the universe discovered in 1999 and the formation of large-scale structures. The former is often explained in cosmological theories by the presence of dark energy , which acts with negative pressure.
DES is operated by an association of scientists at various universities and research institutes in the USA, Brazil, Great Britain, Spain, Germany, Australia and Switzerland. The five-year astronomical observations are carried out at the Cerro Tololo Inter-American Observatory in the Atacama Desert in Chile and cover about an eighth of the sky. DES forms the counterpart to the Sloan Digital Sky Survey in the southern sky, but has better image quality and greater depth.
DECam
The Dark Energy Camera (DECam) is installed at the main focus of the 4-meter Victor M. Blanco telescope at the Cerro Tololo Inter-American Observatory . It has 62 CCDs for scientific observations (each with a resolution of 2048 × 4096 pixels) and 12 auxiliary CCDs. Their total weight is about four tons.
DECam has a total of seven optical filters that cover different wavelength ranges. DES uses the g, r, i, z and Y filters.
Screening
In total, about one eighth of the sky or 5000 square degrees are observed. In each of the five optical filters, ten individual observations should be made over the entire surface. After a verification phase in winter 2012/13, the main observations began in August 2013. At the end of 2016, DES is in its fourth year of observation.
In addition, deeper supernova fields with a total area of 30 degrees are observed.
The area covered by DES overlaps with many other surveys, e.g. B. the South Pole Telescope , the Vista Hemisphere Survey, COSMOS, and SDSS Stripe 82.
Cosmological samples
DES studies a number of cosmological samples, which are briefly described in this section.
Supernovae
Supernovae of type Ia are approximately standard candles . Due to the connection between apparent brightness and redshift , the expansion of the universe can be measured at relatively late times.
Galaxy clusters
Galaxy clusters are the largest observed collapsed objects in the universe. Their density of numbers is predicted by cosmological theories.
Weak gravitational lensing
The weak gravitational lensing effect describes a small, only statistically measurable change in the observed shape and size of background galaxies whose light is deflected by the gravity of astronomical objects (e.g. galaxies and galaxy clusters).
Large-scale structures
The distribution of matter is also predicted by cosmological theories. It is often described by two-point correlations. For this purpose, the positions of astronomical objects (often galaxies) are used as tracers of the non-directly observable matter field.
Further scientific goals and results
- optical follow-up examinations as part of the first observation of gravitational waves
- Discovery of 2014 UZ224 , an asteroid and likely dwarf planet on the edge of the solar system
Web links
Individual evidence
- ^ Collaboration and Sponsors - The Dark Energy Survey . In: The Dark Energy Survey . ( darkenergysurvey.org [accessed December 15, 2016]).
- ↑ David Gerdes: 2014 UZ224. In: www-personal.umich.edu. Retrieved December 15, 2016 .